Bugbear Bubbles is the home of Gelatinous Cube soap. They put dice in soap and sell the resulting squares to gamers.
Initially inspired by Xanathar's pest goldish Sylgar, but then adopted by Critters and Marisha Ray's Keyleth character, the Keyfish has found critical success.
The seven dice come in a Cyberpunk Red styled packet and will cost you £12.79.
It's not a spellbook, though. It's not even a book. It's a tabletop gamer's kit.
Risking WotC legal wrath, Unbalanced Games has a great looking/ugly dice. It's a Beholder in a d20.
You get to pick the art that appears in the base, as you do the colour of the material (I think a gold spellcircle on a crimson base works for me), and then you get to pick your frame for the accent.
Do you use dice to keep track of your current hit points? It's a common approach because it's fast, effective, and an excuse to keep dice around.
To be clear, Tiny Cthulhu isn't about small and cute cosmic horror.
Most gamers roll two ten-sided dice where one dice counts for the tens and the other for the singles.
Did you know your life might be better if it had a glowing polyhedron on your desk?